A study will be made of the development of the eye lens from early embryonic stages on in the normal mouse and in strains with genetic mutations leading to lens abnormalities (Cataract-Fraser; lens rupture; aphakia). Histological, electron microscopic and autoradiographic, as well as immunological and electrophoretic methods will be employed. Comparable studies will be carried out on chicken embryos. It is hoped that this study will lead to better understanding of the genetic regulation of lens differentiation and of the causes of hereditary eye abnormalities.